1. Field of the Invention
The present invention relates to an electric rotary machine (hereinafter referred to as xe2x80x9crotary machine,xe2x80x9d or occasionally xe2x80x9cmotorxe2x80x9d as appropriate), and more particularly to a radial gap type rotary machine comprising an armature with discrete salient poles.
2. Description of the Related Art
In a conventional rotary machine including a stator armature structured such that a plurality of ring-shaped yoke pieces, which are made of a soft magnetic plate, such as a silicon steel plate, and which each have a plurality of pole tooth portions protruding radially, are stacked in the axial direction, since each of the ring-shaped yoke pieces is punched out integrally with the plurality of pole tooth portions as a single piece (the armature composed of the ring-shaped yoke pieces thus structured is hereinafter referred to as xe2x80x9cintegral armaturexe2x80x9d as appropriate), pole teeth each composed of a stack number of pole tooth portions are not partitioned structurally and therefore a resultant armature will have superior magnetic efficiency (low reluctance). However, in a small rotary machine, since a wire is usually wound directly on each of the pole teeth, the integral armature makes the winding operation troublesome, and extremely troublesome when the rotary machine is of inner rotor type. As a result, the winding operation takes a long time, and the winding incurs unsatisfactory space factor as well. And, due to the flyer-winding involved in this case, the wire is subject to torsional stress during the winding operation, thereby failing to ensure reliability of the winding area.
Under the circumstances above described, a rare earth magnet having high energy product has been developed recently, and the structure of a rotary machine can be reviewed by means of magnetic circuit analysis using a computer. This works to enable a rotary machine with an armature of discrete salient pole structure (this armature is hereinafter referred to as xe2x80x9cdiscrete armaturexe2x80x9d as appropriate) to obtain requisite motor characteristics. The rotary machine with the discrete armature may give some undesired increase in reluctance but offers great advantages of easier winding operation and increased space factor of winding so as to override the disadvantageous increase in reluctance. From this, it is now realized that the rotary machine with the discrete armature produces higher performance and is manufactured less expensively on the whole, and there is a growing demand for the discrete armature.
One example of the discrete armature is manufactured such that pole tooth portions are dismembered off its main body portion of an integral armature, a wire is wound around each of the dismembered pole tooth portions thereby constituting each salient pole portion, and that the pole tooth portions each with a wire wound therearound, namely, the salient pole portions are rejoined to the main body portion by laser-welding, or the like.
The armature thus structured, however, has a disadvantage that the integral armature has to be first sectioned and later reassembled, thereby requiring an additional time. Also, when the pole tooth portions each with a winding (salient poles) are rejoined to the main body portion, the stack layers of the both portions have to be matched with each other, and therefore it is required that respective portions be held together by a well-maintained tool and surely welded plate by plate for ensuring precision, which results in decreased workability. And, joints (welded portions) deteriorate significantly in mechanical strength and magnetic characteristics.
To overcome the above described problems, the present inventors disclosed in Japanese Patent Application Laid-open No. 2001-238377 a radial gap type rotary machine including a stator which comprises: a discrete armature including a plurality of discrete salient poles, and a cylindrical pole tooth ring for connecting the salient poles to one another magnetically and mechanically; and a cylindrical stator ring adapted to decrease leakage flux resulting from magnetic discontinuity.
FIG. 10 is a partial cross-sectional view of a conventional rotary machine with a discrete armature viewed from the axial direction. Illustrated in FIG. 10 are: salient poles 106, an armature assembly 110, a flange 12, a rotor assembly 20, a shaft 21, pole teeth 134, bobbins 136, bobbin flanges 136b and 136c, coil winding portions 136g, magnetic wires 138, a molding resin 60, and a stator ring 100. The rotary machine disclosed in the above mentioned Japanese Patent Application Laid-open No. 2001-238377 has a pole tooth ring for positioning and fixing salient poles, but the pole tooth ring is not essential for the prevent invention and is omitted in FIG. 10 for ease of understanding. However, it is noted that the present invention can be applied to a rotary machine having the pole tooth ring.
As shown in FIG. 10, in the conventional rotary machine with a discrete armature, the bobbin 136, which holds a pole tooth comprising a plurality of thin steel plates stacked, has its flanges 136b and 136c respectively on its both ends sandwiching the coil winding portion 136g. The bobbin flanges 136b and 136c are dimensioned to be larger than the coil winding thickness so as to keep the magnet wire 138 braided in good shape. And, the molding resin 60 is injected between the salient poles 106, whereby the salient poles 106 and the magnet wires 138 are fixed securely. The above described rotary machine, however, has the following problems.
The circumferential dimension of the bobbin flange 136b positioned toward the stator ring 100 is usually determined according to the coil winding thickness. The magnet wire 138 receives a stress due to the expansion and contraction of the molding resin 60 injected between the salient poles 106, and may become unbraided at its outer turns when the bobbin flange 136b is conventionally dimensioned, which allows a part of the magnet wire 138 to get in direct contact with the stator ring 100 of a steel plate, possibly causing an insulation failure.
Also, the bobbin flange 136b has a dimensional problem, which will be described with reference to FIGS. 11A, 11B and 12.
FIG. 11A is a cross-sectional view of a bobbin of the salient pole 106, in which the bobbin flange 136b positioned toward the stator ring 100 is dimensioned to the outside dimension of a coil, and FIG. 11B is a cross-sectional view of a bobbin of a salient pole 206, in which a bobbin flange 236b positioned toward the stator ring 100 is dimensioned to be larger than the outside dimension of a coil.
Referring to FIG. 11B, the bobbin flange 236b dimensioned to be larger than the outside dimension of a coil is forced to be located closer to another bobbin flange 236c due to the stator ring 100 arcing, thereby decreasing a winding space for a magnet wire 238. This means that, if a bobbin flange positioned toward the stator ring 100 is simply increased in dimension as shown in FIG. 11B for the purpose of preventing the coil from getting unbraided resulting in a magnet wire coming in contact with the stator ring 100, the winding space is decreased resulting in a reduced space factor, thereby failing to achieve desired motor characteristics. Seemingly, this problem can be solved by making the bobbin flange 236b configured, specifically, arced to the configuration of the inner circumferential surface of the stator ring 100, but this seeming solution still has the following problem.
FIG. 12 is an explanatory view of the problem of the seeming solution. In FIG. 12, a salient pole 306 has a bobbin with a bobbin flange 336b located toward the stator ting 100 (not shown in FIG. 12). The bobbin flange 336b has an increased dimension, and is arced to follow the inner circumferential surface of the stator ring 100. With this configuration, a coil winding portion 336g defined by a space between the bobbin flange 336b and another bobbin flange 336c can be increased by the dimension S in the length direction. However, the inwardly-overhanging (downwardly in the figure) ends of the bobbin flange 336b stand in the way when a magnet wire 338 is wound on the bobbin, making the winding operation very difficult, and can touch the magnet wire 338 causing a trouble. Accordingly, the increased dimension S cannot be fully utilized due to the existence of the downwardly-overhanging ends of the bobbin flange 336b. 
Further, the rotary machine shown in FIG. 10 is structured such that-the rotor assembly 20 is disposed at the center of the stator ring 100, and a plurality (six in the figure) of salient poles 106 are arrayed circumferentially between the stator ring 100 and the rotor assembly 20. This structure causes it that an open space, into which the molding resin 60 is poured, is larger toward the stator ring 100 than toward the rotor assembly 20. In this structure, the above described problem produces an additional open space proportionate to the decreased coil winding portion, which increases the amount of the molding resin 60 thereby pushing up the material cost and increasing the injecting time, especially in case of a large size rotary machine.
The present invention has been made in the light of the above problems, and it is an object of the invention to provide a rotary machine, in which a magnet wire is free from contact with a stator ring, the space factor of a coil is increased, and the amount of a molding resin to be injected inside the stator ring is decreased.
In order to achieve the object, according to a first aspect of the present invention, a rotary machine includes a stator comprising: a stator ring thereby forming a magnetic circuit; a plurality of salient poles each having a pole tooth, disposed inside the stator ring, and fixed by a molding resin injected inside the stator ring; and a plurality of bobbins each constituting the salient pole, adapted to lodge the pole tooth fitted thereinto and to have a magnet wire wound thereon, and each having its outward-positioned flange in contact with the stator ring, wherein the outward-positioned flange has two flexible thin-walled extensions at its respective ends thereby securely holding the wound magnet wire in place.
According to a second aspect of the present invention, in the rotary machine of the first aspect, a resin compartment is formed at the end of one of the two thin-walled extensions.
According to a third aspect of the present invention, in the rotary machine of the second aspect, any part of the resin compartment is positioned behind the plane of the inner wall face of the bobbin flange before assembly.
According to a fourth aspect of the present invention, in the rotary machine of the second or third aspect, the resin compartment is hollow.
Accordingly, in the rotary machine of the present invention, the flexible thin-walled extensions, which are adapted to hold the magnet wire wound in place thereby preventing the magnet wire from making contact with the stator ring, stay unbent before assembly and are bent during assembly, whereby the winding operation is not hindered improving the production efficiency and also the coil winding portion can be successfully increased improving the space factor. And, the resin compartment works to reduce the open space in the stator ring to be filled by the molding resin, thereby decreasing the amount of the molding resin and reducing the time for injecting the molding resin.